1. Field of the Invention
The invention relates to a cylinder lock assembly, and more particularly to a handle-returning device, which can rotate along with a tubular spindle of a cylinder lock assembly when a handle is rotated, and which can return the handle to an original rest position.
2. Description of the Related Art
Cylinder locks typically include a latch operator to operate a latch, a tubular spindle connected to an operating lever handle or knob to actuate a latch operator, and a handle-returning device that is rotatable along with the tubular spindle and that includes a torsion spring to return the operating lever handle or knob to an original rest position thereof. When the operating lever handle or knob is rotated, the tubular spindle operates the latch operator to retract the latch, and at the same time rotates the handle-returning device. When the operating lever handle or knob is released, the torsion spring of the handle-returning device returns the operating lever handle or knob to the original rest position.
Generally, the handle-returning device has a rotating member disposed around and in engagement with the tubular spindle for simultaneous rotation. Like the operating knob, the operating lever handle has a casing body surrounding the tubular spindle. Examples of cylinder lock assembles having lever handles are disclosed in U.S. Pat. Nos. 7,137,657, 5,666,833, 7,073,829. Because the operating lever is heavier than the operating knob and has an L-shaped configuration with a center of gravity usually eccentric to the axis of the tubular spindle, compared to the operating knob, the operating lever handle can impose a relatively high torsional stress on the tubular spindle and the handle-returning device. As a result, after a long time of use, the operating lever handle is prone to droop, and the torsional spring is liable to fatigue failure losing its capability to return the lever handle to its horizontal rest position. When a large force is applied to the lever handle, the tubular spindle can become twisted, or even break.